350 



ARACHNIDA ARAN EAE 



CHAP. 



not belong to the Epeiridae but to the cribellate Uloboridae, but 

 its defective orb -web is so curious that it deserves a special 

 mention. A single foundation -line is laid clown, and from it 



four radii are drawn 

 and are connected 

 with cross lines, the 

 snare constituting 

 about one -sixth of 

 a circle. From the 

 centre of the incom- 

 plete circle a thread 

 proceeds to some 

 more or less distant 

 object, and on this 

 the spider takes up 



B 



its position, inverted, 

 and hauls in the line 



Fn;. 11*1. A, Snare of Hyptiotes cavatus ; B, enlarged till the Sliare IS taut, 

 view of the Spider, showing the "slack" of the "\yhen the tl'emblim>- 

 hauled-in line. (After Emerton. ) 



of the line shows the 



spider that an insect has struck the net, it lets go with its fore 

 legs, and the web, springing back to its normal position, entangles 

 the intruder more thoroughly by its vibrations. When large 

 insects are in question the spider has been observed to " spring " 

 the net several times in succession. H. cavatus is common in 

 tlif pine woods of Pennsylvania, but the only English species, 

 H. paradoxus, is extremely rare. 



A remarkable spider has been discovered in Texas by 

 AlTook, which, after building a horizontal orb-web, converts it 

 subsequently into a dome (Fig. 192) of exceedingly perfect form. 

 It is named ti/if/rtt basilica, and has been the object of careful study 

 by I>r. .Marx, who observed the whole process of web-construction. 

 Th reads are attached at various points on the upper surface of 

 the horizontal wheel, the central portion of which is gradually 

 ] nilled up until the height of the dome is nearly equal to the 

 diameter of its base. P>ut the snare of this spider does not 

 consist of the dome alone. A sheet of irregular lines is stretched 

 lielow, while above there is a maze of threads in the form of a 

 pyramid. Several other Orb-weavers, as, for instance, E. lali/- 

 and K. lri/irnea, supplement their typical webs by an 



